Activates HECT domain-containing E3 ubiquitin-protein ligases, including ITCH, NEDD4, NEDD4L, SMURF2, WWP1 and WWP2, and consequently modulates the stability of their targets. As a result, may control many cellular processes. Recruits ITCH, NEDD4 and SMURF2 to endosomal membranes. Negatively regulates KCNH2 potassium channel activity by decreasing its cell-surface expression and interfering with channel maturation through recruitment of NEDD4L to the Golgi apparatus and multivesicular body where it mediates KCNH2 degradation (PubMed:26363003). May modulate EGFR signaling. Together with NDFIP1, limits the cytokine signaling and expansion of effector Th2 T-cells by promoting degradation of JAK1, probably by ITCH- and NEDD4L-mediated ubiquitination (By similarity). {ECO:0000250|UniProtKB:Q91ZP6, ECO:0000269|PubMed:12761501, ECO:0000269|PubMed:19343052, ECO:0000269|PubMed:20534535, ECO:0000269|PubMed:26363003}. This is the function of NDFIP2 (Nedd4 family interacting protein 2, Ensembl gene identifier ENSG00000102471).